The objectives of the proposed studies are to quantitatively describe the control characteristics of pulmonary and systemic hemodynamics by the arterial baroreceptors, together with the effects of the inhalational anesthetic agents halothane nitrous oxide upon these relationships. In addition the reflex control of cardiopulmonary hemodynamics in the awake and anesthetized dog will be studied during the evolution of an induced systemic renal hypertension. Electromagnetic flow probes will be chronically implanted on the main pulmonary artery and the ascending aorta. By means of a pneumatic occulsion device on the brachiocephalic artery, carotid sinus hypotension will be produced. From the aortic and pulmonary artery pressure and flow responses, values of aortic and pulmonary input impedance will be determined, together with the various components of the corresponding hydraulic power. The pulmonary and systemic responses to brachiocephalic occulsion will subsequently be studied in the above dogs during halothane anesthesia with end-tidal halothane concentrations varying from approximately 0.5-1.5 MAC, with and without 67% nitrous oxide. As a terminal procedure mean carotid sinus pressure will be changed in the isolated sinuses before and after division of the aortic depressor nerves and following bilateral cervical vagotomy to eliminate aortic baroreceptor afferents and any remaining cardiopulmonary vaga afferents, respectively. The above acute and chronic studies will subsequently be repeated in dogs in which systemic hypertension has been induced following unilateral renal artery constriction and in a further group of dogs in which the affected kidney has been removed and a remission of the systemic hypertension has occurred.